Boesmansgat, also known in English as “Bushman’s Hole“, is believed to be the sixth-deepest submerged freshwater cave (or sinkhole) in the world, having been dived to 282.6 metres (927 ft). It is located in the Northern Cape province of South Africa.
Boesmansgat was believed to have first been explored by amateur diver Mike Rathbourne, in 1977. The lowest depth attained was by Nuno Gomes, in 1996. Its altitude of over 1,500 metres (4,900 ft) makes this a particularly challenging dive, requiring a decompression schedule equivalent for a dive to 339 metres (1,112 ft) feet at sea level. (Gomes’ dive was a close call, as he got stuck in the mud on the bottom of Bushman’s Hole for two minutes before escaping.)